Golf ball

ABSTRACT

The invention provides a golf ball characterized by having a surface over all or part of which is provided a major region colored a dark color and, in the major region, indicia such as letters and images of a relatively bright color tone, wherein the dark color of the major region, as expressed by the Lab color system, has a lightness L of at most 45 and a chroma C, defined as (a 2 +b 2 ) 1/2 , of at most 5. The golf ball of this invention is colorful and highly fashionable while retaining an excellent rebound and scuff resistance.

BACKGROUND OF THE INVENTION

The present invention relates to golf balls having a colored surface, and more specifically to golf balls that are highly fashionable and have excellent visibility, rebound and scuff resistance.

Most golf balls are colored white, although colored golf balls obtained by applying a bright color other than white, such as orange or yellow, to the surface of the ball have also appeared on the market.

Consumers of various types are playing golf nowadays, and even the number of women golfers is increasing from year to year. Colored balls such as those described above respond to the desires that such golfers have concerning the white balls that are conventionally used. Namely, colored balls have the advantage of being highly fashionable on account of their color. In addition, by imparting a color sensation, they readily attract one's attention.

However, in prior-art colored golf balls, only the appearance of the ball has been changed; the performance of such ball remains substantially unchanged from that of white golf balls.

In light of these circumstances, the object of the present invention is to provide golf balls which are endowed with the outstanding ball performance that has come to be expected of golf balls and which are also highly fashionable and have excellent visibility.

SUMMARY OF THE INVENTION

We have carried out extensive investigations in order to attain the above object. As a result, we have discovered that by forming over all or part of the surface of a golf ball a major region colored a dark color and, in the major region, indicia such as letters and images of a relatively bright color tone, and by adjusting the tone of the dark color in the major region such that the dark color, as expressed by the Lab color system, has a lightness L of at most 45 and a chroma C defined as (a²+b²)^(1/2) of at most 5, there can be obtained golf balls which have improved ball characteristics such as rebound and scuff resistance, and which are also colorful and highly fashionable. This discovery led ultimately to the present invention.

Accordingly, the invention provides the following solid golf balls.

-   -   (1) A golf ball characterized by having a surface over all or         part of which is provided a major region colored a dark color         and, in the major region, indicia such as letters and images of         a relatively bright color tone, wherein the dark color of the         major region, as expressed by the Lab color system, has a         lightness L of at most 45 and a chroma C, defined as         (a²+b²)^(1/2), of at most 5.     -   (2) The golf ball of (1) above, wherein the major region is         black in color.     -   (3) The golf ball of (1) above, wherein the color of the major         region and the color of the indicia have a Lab color difference         ΔE of at least 30.     -   (4) The golf ball of (1) above, wherein the color of the major         region and the color of the indicia have a difference in         lightness L therebetween of at least 25.     -   (5) The golf ball of (1) above, wherein the indicia are composed         of a plurality of colors.     -   (6) The golf ball of (1) above, wherein a plurality of indicia         are formed on the surface of the ball.     -   (7) The golf ball of (6) above, wherein the indicia are         substantially uniformly dispersed and positioned on the surface         of the ball.     -   (8) The golf ball of (1) above, wherein the major region and the         indicia each have a surface area coverage based on the entire         surface of the ball such that the ratio of the major region         surface area coverage to the indicia surface area coverage is         from 70:30 to 99:1.

BRIEF DESCRIPTION OF THE DIAGRAMS

FIG. 1 is a top view of the surface of a golf ball according to one embodiment of the invention.

FIG. 2 is a cross-sectional view of the ball shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described more fully below.

The inventive golf ball is characterized by having formed, over all or part of the surface thereof, a major region which is dark colored, such as black, and by having formed in the major region indicia of a relatively bright color tone. FIG. 1 is a top view of the surface of a golf ball according to a first embodiment of the invention. In FIG. 1, G represents the golf ball, T is an indicium, and W is a major region on the surface of the ball. This region has a dark color.

In the present invention, the golf ball is characterized in that the dark color of the major region W, as expressed using the Lab color system, has a lightness L of at most 45 and a chroma C, defined as (a²+b²)^(1/2), of at most 5.

The Lab color system used herein is determined from the following expressions using the tristimulus values X, Y and Z specified in JIS Z8730. L=10Y ^(1/2)   (1) a=17.5(1.02X−Y)/Y ^(1/2)   (2) b=7.0(Y−0.847Z)/Y ^(1/2)   (3)

Here, L is the lightness index in R. S. Hanter's color difference equations. The color coordinates in Hunter's color difference equations are as follows: a, b: color coordinates in Hunter's color difference equations; X, Y, Z: tristimulus values X, Y and Z in XYZ color system.

Of the above Lab color system, L represents lightness and is determined as a value from 100 to 0. “Lightness” refers to the light or dark state of the color; that is, to the degree of luminance. A larger L value signifies greater lightness.

The a and b values indicate perceived color, with the a value representing the red-green direction and the b value representing the yellow-blue direction. Therefore, when the a value becomes larger the redness intensifies, and when it becomes smaller the greenness intensifies. When the b value becomes larger, the yellowness intensifies, and when it becomes smaller the blueness intensifies. The relationship between these a and b values is summarized in Table 1 below. TABLE 1 b a Minus (−) Close to zero Plus (+) Minus (−) blue blue-violet violet Close to zero green white/gray/black red-violet Plus (+) blue-green yellow red

In the practice of the invention, the major region W in areas other than where there are indicia T has a color lightness L of at most 45, preferably at most 40, more preferably at most 35, and even more preferably at most 30.

The larger the numerical value of the chroma C, the more vivid the color. Conversely, the smaller the numerical value, the more somber the color. At a value close to 0, the color becomes grayish. In the practice of the invention, the chroma C of the color of the major region W is at most 5, preferably at most 4, more preferably at most 3, and most preferably at most 2.

The Lab color differences (Hunter Lab color differences) for the color of the major region W and the color of the indicia T are each determined, and the color difference ΔE between the two is computed. That is, the Lab color difference (L1, a1, b1) for the major region and the Lab color difference (L2, a2, b2) for the indicia are each measured. The differences therebetween, ΔL=L1−L2, Δa=a1−a2, Δb=b1−b2, are then computed, and the color difference ΔE between the two colors is determined from the following formula. ΔE =(ΔL²+Δa²+Δb²) 1¹²

The color difference ΔE here is at least 30, preferably at least 35, more preferably at least 40, and even more preferably at least 50. At a color difference ΔE of less than 30, the colors of the major region W and the indicia become similar, which may lower the visibility of the indicia T.

The upper limit in the color difference ΔE is not subject to any particular limitation. However, from an aesthetic standpoint in golf ball production, ΔE is not more than 150, preferably not more than 120, and more preferably not more than 100.

The indicia T are exemplified by trademarks and abbreviations composed of characters such as letters, numbers, kanji characters, kana characters or symbols and of various images. In terms of the aesthetic appearance of the ball, the color of the indicia T may be selected as appropriate based on, for example, the color used for indicia such as the play number and the darkness of the color of the major region on the ball's surface.

The indicia T may be single-colored, although a plurality of different colors, such as a combination of two to four colors, may be arranged for the purpose of adding more aesthetically pleasing elements. In such a case, to the extent possible, it is preferable to arrange the colors uniformly over the entire spherical surface.

In FIG. 2, the above-described indicia T are shown formed at mutually opposing positions (front side and back side) on the surface of the ball. The ball G in FIG. 2 has a two-layer construction. Also represented by symbols in FIG. 2 are a solid core 1, a cover 2, and dimples D.

The dark-colored region and indicia portions of the golf ball's surface each have a surface area coverage relative to the entire spherical surface of the inventive ball such that the ratio therebetween, expressed on the basis of the dark-colored region, is at least 70:30, preferably at least 80:20, and more preferably at least 90:10, with an upper limit of 99:1 or less, preferably 98:2 or less, and more preferably 95:5 or less. If the ratio of the dark-colored region is less than 70:30, the aesthetics of the golf ball may be compromised. On the other hand, at more than 99:1, visibility of the ball may become a problem.

In the practice of the invention, the type and construction of the golf ball are not subject to any particular limitations. That is, the golf ball core enclosed within a cover is not subject to any particular limitation. Thus, the golf ball may be a thread-wound golf ball containing a thread-wound core. On the other hand, if the golf ball is one which contains a solid core, the ball may have a layer construction that is one-piece, two-piece or multi-piece with more than two pieces. The thread-wound core and solid core can be used in the same way as a conventional thread-wound core or solid core. Cores obtained with known materials and by conventional methods may be used.

The cover stock may be, for example, an ionomer resin, a polyester elastomer or a thermoplastic or thermosetting polyurethane elastomer, either by itself or as a resin mixture in combination with another resin such as a polyamide resin or an ethylene-vinyl acetate copolymer.

Other ingredients such as titanium oxide, barium sulfate, dispersants, carbon black, various pigments, polyethylene wax and tungsten may be suitably blended into the above cover composition. The Lab color of the cover can be adjusted to the optimal color by adjusting the amounts in which these ingredients are compounded.

The above-described golf ball can be manufactured by a known process. For example, if the ball is a two-piece or multi-piece solid golf ball, advantageous use can be made of a known process in which a solid core that has been molded under heat is placed in a given injection molding mold, following which a certain technique is used to inject the above-described cover stock around the core in the case of a two-piece solid golf ball, or to successively inject a mantle material and the cover stock in the case of a multi-piece solid golf ball. In some cases, the cover stock can be manufactured by molding under applied pressure.

A known method may be used to form the indicia. Specific examples of methods that may be advantageously used for this purpose include stamp printing, ink jet printing and the use of special inks which produce a color upon exposure to special light such as ultraviolet light.

Characteristics of the inventive golf ball such as its weight and diameter may be suitably selected in accordance with the Rules of Golf.

The surface of the inventive golf ball may be painted, in which case painting may be carried out with a commonly used paint. However, by painting the surface of the ball a color other than white, and specifically one having a lightness L of 45 or less, and by including in the paint various polarizing materials, the ball's surface can be made more lustrous, enabling the appearance of the ball to be better finished than if a polarizing material is not included. Specifically, the interference effect by light reflected from the polarizing material causes color flop to occur, enabling a highly fashionable and stylish ball appearance to be achieved. An illustrative example of such a paint is that obtained by including 1.25 wt % of the polarizing material Iriodin 153 (available from Merck) in a two-component curable urethane coating having a solids content of 35%.

The golf balls of the invention are thus colorful and highly fashionable while maintaining excellent rebound and scuff resistance.

EXAMPLES

Examples of the invention and Comparative Examples are provided below to illustrate the invention and are not intended to limit the scope thereof.

Examples 1 to 10, Comparative Examples 1 to 5

A rubber composition formulated as shown below was mixed in a roll mill, then heat compression molded to form a solid core of 40.3 mm diameter.

Rubber Composition: cis-1,4-Polybutadiene 100 parts by weight Zinc acrylate 25 parts by weight Zinc oxide 14 parts by weight Antioxidant 0.1 part by weight Dicumyl peroxide 1.5 parts by weight

In each example, the cover stock shown in Table 2 was injection molded around the resulting core so as to enclose the core, thereby fabricating a 42.7 mm diameter two-piece golf ball having a 1.2 mm thick cover layer. TABLE 2 Cover stock (pbw) A B C Polyurethane T8295 ¹⁾ 50 50 50 Polyurethane T8260 ²⁾ 50 50 50 Carbon black 0.3 0 0 Titanium oxide 0 3.0 0.1 Polyethylene wax 1 1 1 Dioxazine 0 0 1 ¹⁾ Polyurethane T8295: An MDI-PTMG type thermoplastic polyurethane produced by DIC Bayer Polymer, Ltd. ²⁾ Polyurethane T8260: An MDI-PTMG type thermoplastic polyurethane produced by DIC Bayer Polymer, Ltd.

A golf ball according to this invention (Example 1) and a white golf ball known to the art (Comparative Example 1) were both exposed to direct sunlight for a given length of time, and the resulting temperature change at the ball's surface as well as the rebound and scuff resistance following the temperature change were evaluated. Those results are shown in Table 3 below.

Rebound Performance:

The ball being tested was exposed to sunlight for 180 minutes, following which the initial velocity when struck at an impact speed of 43.83 m/s (143.8 ft/s) was measured using a USGA-approved drum rotation-type initial speed measuring device.

Scuff Resistance:

The ball being tested was exposed to sunlight for 180 minutes, then struck twice each at a head speed (HS) of 33 m/s with two clubs: an Eagle pitching wedge (manufactured by Bridgestone Sports Co., Ltd.) and a Gravistar pitching wedge (manufactured by Spalding Company) on a swing machine. The appearance of each ball was then inspected by three judges. A higher numerical value indicates better scuff resistance. TABLE 3 Comparative Example 1 Example 1 Difference Cover stock A B Color black white L 26.7 90.2 a −0.3 −0.9 b −0.5 −10.4 Chroma C 0.6 10.4 Temperature Initial 24.0 24.0 0 (30° C.) After 5 minutes 25.2 24.3 0.9 After 10 minutes 26.4 24.9 1.5 After 15 minutes 27.1 25.1 2.0 After 60 minutes 31.6 28.4 3.2 After 180 minutes 41.5 32.5 9.0 Rebound (initial velocity), m/s 77.3 76.6 0.7 Scuff resistance 5.1 3.7 1.4 Lab color measurement: Chroma C = (a² + b²)^(1/2) using a multiple light source spectrocolorimeter (Suga Test Instruments Co., Ltd.).

Next, golf balls in Examples 2 to 10 and Comparative Examples 2 to 5 were manufactured as examples of the invention and prior-art examples, respectively, in which the color of the indicia provided on the dark-colored region of the ball was varied, thereby changing the color difference. The surface area ratio of the indicia, based on the surface area of the dark-colored region (the region having a black or dark blue color) in each example was 80:20. The visibility of these golf balls was evaluated. The results are shown in Table 4 below.

Visibility:

A panel of 10 judges evaluated the ease with which the indicia formed on the ball's surface can be seen. Visibility was rated based on the following criteria.

-   -   Very Good (VG): Regarded by at least 8 judges as easy to see.     -   Good: Regarded by 5 to 7 judges as easy to see.

Fair: Regarded by 3 or 4 judges as easy to see. TABLE 4 Example Comparative Example 2 3 4 5 6 7 8 9 10 2 3 4 5 Cover stock A A A C A A A A A A A A A Dark-colored Color black black black dark blue black black black black black black black black black major region L 26.7 26.7 26.7 29.9 26.7 26.7 26.7 26.7 26.7 26.7 26.7 26.7 26.7 on ball surface a −0.3 −0.3 −0.3 10.4 −0.3 −0.3 −0.3 −0.3 −0.3 −0.3 −0.3 −0.3 −0.3 b −0.5 −0.5 −0.5 −28.8 −0.5 −0.5 −0.5 −0.5 −0.5 −0.5 −0.5 −0.5 −0.5 Chroma C ¹⁾ 0.6 0.6 0.6 30.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Indicia Color silver gold white white yellow green pink violet red brown gray green blue L 81.9 67 92.1 92.1 93.4 74.1 70 30.6 39.8 29.1 32.1 38.2 35.1 a 0.5 2.3 1 1 −1.2 −41.1 84.8 19.9 50.1 4.4 2.3 −20.4 0.9 b −3 21.5 0.7 0.7 60 33.9 −30.2 −37.4 13.4 6.8 −0.1 −2.5 −30 Color difference 55.3 46.0 65.4 69.5 90.1 71.4 100.0 42.2 53.9 9.0 6.0 23.2 29.7 ΔE ²⁾ Lightness 55.2 40.3 65.4 62.2 66.7 47.4 43.3 3.9 13.1 2.4 5.4 11.5 8.4 difference ³⁾ Visibility VG VG VG VG VG VG VG good good poor poor poor poor ¹⁾ Chroma C = (a² + b²)^(1/2) ²⁾ Color difference ΔE = (Δh² + Δa² + Δb²)^(1/2) ³⁾ Lightness difference: difference between lightness L of ball surface and lightness L of indicia

As is apparent from the results in Tables 3 and 4, because the major region on the surface of the inventive golf balls has a dark color of optimized tone, exposure to sunlight raises the temperature at the ball's surface. Irradiation for even a relatively short period of time will have a similar temperature-raising effect even on cold days. As a result, the rebound and scuff resistance of the golf ball can be advantageously improved. Moreover, because the inventive golf ball can be conferred with a lightness contrast based on the relatively brightly colored indicia, after the ball has been played, the ease with which the indicia can be seen provides for a high ball visibility to the golfer. It is thus evident that the golf balls of the invention are more beneficial to the golfer than conventional single-colored white golf balls. 

1. A golf ball characterized by having a surface over all or part of which is provided a major region colored a dark color and, in the major region, indicia such as letters and images of a relatively bright color tone, wherein the dark color of the major region, as expressed by the Lab color system, has a lightness L of at most 45 and a chroma C, defined as (a²+b²)^(1/2), of at most
 5. 2. The golf ball of claim 1, wherein the major region is black in color.
 3. The golf ball of claim 1, wherein the color of the major region and the color of the indicia have a Lab color difference ΔE of at least
 30. 4. The golf ball of claim 1, wherein the color of the major region and the color of the indicia have a difference in lightness L therebetween of at least
 25. 5. The golf ball of claim 1, wherein the indicia are composed of a plurality of colors.
 6. The golf ball of claim 1, wherein a plurality of indicia are formed on the surface of the ball.
 7. The golf ball of claim 6, wherein the indicia are substantially uniformly dispersed and positioned on the surface of the ball.
 8. The golf ball of claim 1, wherein the major region and the indicia each have a surface area coverage based on the entire surface of the ball such that the ratio of the major region surface area coverage to the indicia surface area coverage is from 70:30 to 99:1. 